Owl monkeys (Aotus) are highly divergent in mitochondrial Cytochromec Oxidase (COII) sequences

The evolutionary history and differentiation of the owl or night monkeys (Aotus),remain poorly resolved. Variation in pelage and skeletal morphology is relatively minor across their broad range, but cytogenetic studies have revealed that at least 12 karyotypically distinct forms exist, with 2Nchromosome numbers ranging from 46 to 58. We obtained DNA samples from three putative species- A. lemurinus, A. nancymae,and A. azarae-and five karyotypes (I, II, III, IV and VI), amplified the mitochondrial cytochrome coxidase subunit II gene (COII) via PCR and sequenced it. Comparisons of the sequences indicate relatively high levels of sequence divergence among the putative species (4.3 to 6.3%), and suggest that the taxa are genetically quite distinct and have likely experienced extended periods of isolated evolution. The levels of COII divergence represent approximately one- third of the levels found between divergent platyrrhine genera, such as Aotus, Saimiriand Callimico.Using estimates of substitution rates of COII evolution in hominoid primates,the estimated date of divergence for the AotusCOII sequences is 3.6 million years. The AotusCOII data support the existence of multiple species of Aotus,with origins predating late Pleistocene climatic events. Although A. nancymaeand A. azaraeboth live south of the Amazon River and have been considered members of the same species group, phylogenetic analysis of the COII sequences does not support a close relationship between them.